This invention relates to ink formulations for use in printing polyvinyl butyral sheets particularly sheets that are to be laminated and used as safety glass interlayers and particularly windshield interlayers provided with a gradient color band to reduce glare.
One of the problems that has to be confronted in dealing with polyvinyl butyral sheet is that when wound onto rolls after production it tends to stick to adjacent laps on the roll making separation difficult. This is known as "blocking" and can also occur when two flat sheets are laid one on top of the other.
The printing of polyvinyl butyral sheets is usually accomplished using an ink formulation comprising a dye and a solvent and an additive to raise the viscosity to a level appropriate for the intended printing operation. This may be a relatively low value as for example in ink-jet or electrostatic mist printing, or a relatively high value as for example in rotogravure printing. Whatever the required viscosity the most practical way of achieving the adjustment is by the addition of a high molecular weight compound that is soluble in the ink solvent and is not incompatible with any other component of the ink.